Cyclone separator with two separating zones and static guide mechanisms

ABSTRACT

Cyclone separator with two separating zones and static guide mechanisms. As a result of an immersion tube column (5, 6, 7), which surrounds the cyclone axis (1) over the entire separating zone height h, which is arranged in the vortex core of the conventional cyclone and passes through the conventional solids collecting container (2a), both the outer swirling flow in the outer separator zone (3a) and also an inner swirling flow concentrated in the immersion tube column in the second separating zone (3b) is stabilized in combination with a return flow-free solids discharge device (4), so that in the case of an intense swirl a following separating process takes place with axial return flows (18) from swirl promoter (17) into a second solids collecting container (2b). The components of the immersion tube column are the conventional immersion tube (5), a downwardly located slotted slit immersion tube (6) in the axial extension thereof and a downwardly following central immersion tube (7), to which is flanged the second solids collecting container (2 b). The sucking slit immersion tube (6) is used as the inflow guide mechanism for the swirl promoter (17) and has four parallel-wall, curved intake channels (10) uniformly distributed about the immersion tube circumference with in each case a straight leading edge (9), which exert an accelerating action on the flow. The recovery of the kinetic energy of the swirling flow is brought about by an outflow spiral (8) above the cyclone cover (13).

The invention relates to a cyclone separator with two separating zonesand static guide mechanisms for improving the separating capacity withrespect to very finely dispersed particles from flowing gases and forreducing the pressure drop or for influencing the field of flow of aconventional centrifugal force separator with a tangential, spiral orhelical intake channel, with a cyclone casing which is cylindrical atthe top and conical at the bottom, as well as a solids collectingcontainer positioned below it, a cylindrical immersion tube for removingthe pure gas flow projecting centrally from above into the cyclonecasing within the cylindrical separating zone.

In a centrifugal force separator, the inflowing feed is separated as aresult of the centrifugal forces occurring in a swirling flow, which acton the particles flowing in circular or spiral paths. As a result of theaxial velocity component of the field of flow, the separated coarsematerial slides in spiral manner on the cyclone outer wall into thesolids collecting container, which forms the lower termination of thecyclone casing. The unseparated fine material passes with the gas flowflowing out through the immersion tube into the clean gas channel.

The simple operation of a conventional centrifugal force separatorensures, as is known, a high operating reliability, low maintenanceexpenditure, low prime costs and limited space requirements. The limitsof its wide use range are at an operating pressure of 100 bar and gastemperatures of over 1000° C.

However, the use advantages of a conventional cyclone must be consideredagainst the disadvantages of the high pressure drop and low separatingcapacity with respect to the separation efficiency compared with otherseparators. Known conventional cyclones have as the main cause of thelow separating capacity an irregular, axial velocity distribution alongthe interface, secondary flows, short-circuit flows and strongturbulence within the separating zone. The main cause of the highpressure drop is the non-conversion of the energy of rotation necessaryfor separation into pressure energy, due to deflection losses and arestricting action at the immersion tube inlet, so that up to 90% of thetotal pressure drop occurs in the vortex core (cyclone eye) below theimmersion tube.

As a result of the requirement of limiting emissions of dust which canenter the lungs, the recovery of valuable products or the maximumseparation of abrasion dust from process gases, as well as for energyreasons, the conventional cyclone must be increasingly combined withother separating means, which are more efficient in finely dispersedparticle size ranges below 20 μm. These requirements and the fact thatthe cyclone is the only industrially usable separator for removing dustfrom hot gases at above 500° C., require additional constructionalmeasures for improving the separating capacity and for reducing thepressure drop.

For fulfilling these requirements, it is known to install guidemechanisms in the separating zone or within the immersion tube, but thehitherto published patent applications do not take account of all thecauses of the low separating capacity and the high pressure drop and nonew cyclone development provides a second separating zoneconstructionally within a single apparatus and additionally makes use ofreturn flows around the cyclone axis for particle separation purposes.

In a known cyclone construction (DE-OS No. 23 61 995), the conventional,cylindrical immersion tube, apart from its axial opening, is provided onthe lower end face with additional slotted gas inlets within theimmersion tube jacket, which are formed by pressed in cover plates ofsaid jacket. The dust removal efficiency cannot be improved, becausesaid slotted immersion tube construction suffers from the importantdisadvantage that neither the strong sink flow below the immersion tube,nor the solids layer flow along the outer immersion tube circumferentialsurface can be reduced and no devices are provided for a followingsolids separation. Devices for recovering the kinetic energy are alsonot provided.

A further cyclone with a slotted immersion tube is known (EP-OS No. 0041 106), which admittedly utilizes the effect of a double separationwith a single apparatus, but without collecting within a secondseparating zone the solids separated within the immersion tube. Aconventional, slotted immersion tube with an axial outflow slit permitsdue to the suction action from the ambient as a result of a slit,located between the inflow channel and immersion tube, the return ofalready discharged fines which have built up on the inner immersion tubewall into the cyclone separating zone. Further disadvantages of thiscyclone construction are the still remaining, axially non-uniformlydistributed sink flow below the immersion tube and the suction ofambient air into the separation process, so that the pressure drop isincreased.

In addition, slotted immersion tubes are described in the journalsChem.-Techn., 22, 1970, No. 9, pp. 525-532 and Maschinenbautechnik 7,1958, No. 8, pp. 416-421. These immersion tube constructions are merelylongitudinal slits arranged uniformly around the immersion tubecircumference and are not edgewise slit channels, which bring about aflow deflection or an energy recovery.

Prof. Schmidt has provided a slotted slit immersion tube(Staub-Reinhaltung der Luft, 45, 1985, no. 4, pp. 163-165 and DE-OS No.32 23 374), which has a helical entrance slit and a three-dimensionaldiffuser channel with deflection characteristics. This so-called helicaldiffuser is closed on the bottom face by a baseplate and is arrangedbelow a conventional immersion tube. This slotted immersion tube reducesthe pressure drop of a cylone separator by up to 50% and improves theseparating capacity of a cyclone, because there is a transition from thecircular hole sink flow to the linear sink flow. However, as the soleconstructional measure, this newly developed immersion tube is not ableto prevent the short-circuit and secondary flows and does not make itpossible to remove the secondary solids separated within the immersiontube. As a result of the diffuser channel incorporated into theimmersion tube, it is not possible to obtain a critical swirling flowwith return flows.

The problem of the present invention, whilst avoiding the describeddeficiencies of conventional cyclones in general and the deficiencies ofknown, improved cyclone constructions with double separation andimproved suction conditions in particular, is to provide a cycloneseparator of the aforementioned type which is so constructionallydeveloped that in the case of simple basic construction and additionalcomponents constituted by static, i.e., non-rotary guide and separatingmechanisms, is characterized by a greatly improved overall and fractionseparation efficiency, so that the separating efficiency of the cycloneseparator is greatly improved, so that there is additionally a reductionin the pressure loss compared with the conventional construction.

According to the invention this problem is solved in that an immersiontube column, comprising the series connection of a conventionalimmersion tube, a slotted slit immersion tube with a helical or straightslit channel and a central immersion tube, which surrounds the cycloneaxis over the entire height of the separating zone, is located in thecylindrical interface of the conventional cyclone separator, passesthrough the conventional solids collecting container and is connected ingastight manner to a second solids collecting container below the firstcontainer, each of the three partial immersion tubes being open at thetop and bottom ends and the slit immersion tube is the sole suckingimmersion tube.

Thus, it is proposed to place the immersion tube column as a secondcyclone within the actual cyclone, so that in this way a two-stageseparation is brought about in a single dust removal apparatus. However,unlike in the external separation process, the mass exchange takes placewithin the swirl promoter by energy transfer via the vortex core aroundthe cyclone axis and return flows bring about the solids transfer intothe secondary solids collecting container below the central immersiontube, if there is a supercritical swirling flow within the swirlpromoter.

It must be borne in mind in connection with the inventive development ofthe cyclone separator, that the downwardly directed axial flow on theouter cyclone jacket in the outer field of flow of the swirling flowbrings about the good discharge behaviour of the solid combined with theinterface flow on the conical wall. In order to bring about an axialvelocity component, the slit immersion tube must be arranged within thecyclone intake channel.

The slotted slit immersion tube is centrally installed in thecylindrical and not in the conical part of the cyclone casing betweenthe conventional immersion tube and the central immersion tube, in orderto reduce secondary flows from the separating wall of the cyclonejacket. The slit immersion tube permits the transition from the holesink otherwise located below a conventional immersion tube with anon-uniform axial distribution of the radial velocity to the linear sinkwith an equalized, axial distribution of the radial velocity on theinterface. The invention is based on the finding that through a slitchannel with a helical leading edge or through several helicallyarranged slit channels with a straight leading edge within the slitimmersion tube, the vortex sink flow in the outer separating zone is notdisturbed or the flow turbulences in the separating zone are reduced andthe volume flow of the gas is sucked at high speed over a curved intakechannel adapted to the flow lines with an accelerating action on theflow in axially uniform manner over the leading edge out of the outerseparating zone, so that there is an equalized velocity profile alongthe suction slit and the dust particles still present in the gas floware concentrated in the wake core about the cyclone axis as a result ofthe compressive forces and are removed with the aid of return flows intothe secondary solids collecting container, so that the separated coarsematerial proportion of the feed increases, which corresponds to animprovement of the overall and fraction separation efficiency.

For stabilizing the two-stage separating process, the immersion tubecolumn is so arranged around the cyclone axis in the vortex core of theconventional cyclone, that is passes through the outer cylindrical andconical separating zone, the cylindrical shielding container and theprimary solids collecting container.

Preferably a baffle is installed in the outer separating zone betweenthe intake channel and the slit immersion tube below the cyclone intakechannel in the horizontal plane parallel to the cyclone cover in such away that short-circuit flows of the swirling flow are directly preventedin the suction slit channel of the slit immersion tube and the axialvelocity component of the swirling flow is positively influenced in theouter separating zone with respect to the solid discharge behaviour.Thus, a breaking away of the cyclone intake flow on the leading edge ofthe cylindrical cyclone jacket is prevented, so that simultaneously thestarting positions of the particles suspended in the entering gas flowis more clearly defined. Thus, the baffle permits a more uniform inflowinto the slit channel of the slit immersion tube.

The slit immersion tube connected in the immersion tube column betweenthe conventional immersion tube and the central immersion tube, can beprovided with parallel-wall intake channels with in each case a straightleading edge uniformly distributed around the immersion tubecircumference, so that the common diagonal of the four recess facesdisplaced by 90% forms a single helical line about the slit immersiontube and the particular curved slit channel in the slit immersion tubeis provided as an intake channel with an accelerating flow action for aswirl promoter symmetrical to the cyclone axis, so that within the swirlpromoter is formed a wake region with axial return flows into thecentral immersion tube in the case of a correspondingly high swirlingintensity, which is fixed by the geometrical design of the slit channeland the slit immersion tube. High vacuum values on the cyclone axis andstrong pressure changes in the axial direction induce the intense returnflow into the central immersion tube and subsequently into the secondarysolids collecting container.

The advantages obtained as a result of the invention are in particularthat through the immersion tube column fixing the interface between thevortex field and the vortex core or through said guide and separatingmechanisms the rigid body vortex (cyclone eye) of the conventionalcyclone separator is concentrated further inwards about the cyclone axisor swirl promoter axis. This rigid body vortex fills up a secondaryvortex or swirling field around it and this is the prerequisite formaintaining the secondary separating process within the swirl promoter.

The slotted slit immersion tube brings about, as a guide mechanism, areinforcement of the vortex or swirling action produced in the cycloneintake in the centre of the swirl promoter. This inner swirling flowaround the swirl promoter axis leads to a wake core about the swirlpromoter axis, whose radius R increases with increasing swirling actionand the particles are "trapped" therein. R₀ consequently indicates thelimit between loss-free healthy flow in the range R₀ <r<R and lossy coreflow in the range R₀ >r>O. There is a strong vacuum in the wake zone, sothat the particles are transferred in the compressive force direction tothe cyclone axis and do not flow in the centrifugal force directiontowards the swirl promoter wall, as is the case in the outer separatingzone. A high R₀ favours the secondary separation effect, because onproducing a critical swirling flow, there is no axially upwardly drivingthrough flow within the wake core which would entrain the particles andinstead there is a negative through flow around the cyclone axis,particularly within the slit immersion tube.

In the second solids collecting container, which is flanged to thecentral immersion tube and arranged below the first solids collectingcontainer, collects the additionally separated solids, transporteddownwards via the central immersion tube with the aid of return flows soas to constitute additional coarse material and which in the case of aconventional cyclone construction would have flowed out via theconventional immersion tube in the form of fines. As a result of theimmersion tube column surrounding the swirl promoter, additionally thethree-dimensional, turbulent field of flow in the outer separating zoneis stabilized, so that the cyclone axis is identical with the centre ofthe outer swirling flow. The centre of the inner swirling flow forms theswirl promoter axis congruent with the cyclone axis and which only inthe case of a symmetrical inflow from the slit immersion tube wouldcoincide with the cyclone axis.

In another construction according to the invention for increasing therotational symmetry and the swirl intensity, the slit immersion tubewith four intake channels helically distributed around the immersiontube circumference can be replaced by a slit immersion tube, which iseither provided with several uniformly distributed slit channelsarranged at the same axial height around the immersion tubecircumference and having straight leading edges, or by a slit immersiontube with parallel-wall, helical slit channel, which has a helicalleading edge and a helical trailing edge, which once again produces asupercritical swirl intensity with return flows into the centralimmersion tube if the particular slit channel is constructed as a curveddeflecting channel with an accelerating action and the particular slitchannel is provided with an upper and a lower coverplate, so that thesuction from the outer separating zone takes place exclusively by meansof a helical slit channel or by means of several slit channels uniformlydistributed in edgewise manner around the immersion tube circumference.

The curved slit channels within the slit immersion tube serve as intakechannels for the swirl promoter arranged symmetrically to the cycloneaxis within the immersion tube column and the swirl promoter ispreferably constructed as a flow-favourable intake guide mechanism foran outflow spiral casing with recess core arranged above the cyclonecover. The kinetic energy of the outer swirling flow and the innerswirling flow in the same direction can be recovered by a wide outflowspiral constructed in known manner and whose outlet connection issuesinto the clean gas channel and whose central wake zone can be filledwithin a widened conventional immersion tube by a corresponding recesscore. Advantageously the intake of the parallel-wall slit channel isconstructed as a slotted opening within the slit immersion tube jacketin such a way that in the intake zone of the slit channel the necessaryflow velocity is obtained on the interface in accordance with the rotarysink flow, which is in turn taken in flow-favourable manner on theinterface as a result of the configuration of the slit immersion tubecircumference as a logarithmic spiral, so that the curved flow lines ofthe gas flow entering the swirl promoter through the slit channel passalong the outer and inner slit channel contours and in the samedirection as the cyclone intake flow.

According to a further development of the invention a cylindricalshielding container is so interposed between the conical part of theouter separating zone and the conventional solids collecting containerthat the outer swirling flow passes out on an outer portion of thecentral immersion tube constructed as a shielding cone within theprimary solids collecting container, so that the separated solids canpass in troublefree manner without any entraining effects in the annularclearance between the cylindrical shielding container and the centralimmersion tube into the primary solids collecting container and thesolids cannot be vortexed again into the outer separating chamberthrough the provision of a conical deflector shield below thecylindrical shielding container and around the shielding cone.

The central immersion tube also permits a pressure-side separation ofthe swirling flow in the outer separating zone from the slightlycirculating flow in the first solids collecting container, in that theshielding cone is arranged within the solids collecting container insuch a way that a penetration of the separated solids into theseparating zone is prevented and simultaneously the penetration of theseparated solids through an annular discharge opening betweencylindrical shielding container and central immersion tube is ensured.The inventive discharge mechanism consequently prevents both a whirlingup again and also an entrainment of already separated particles.

According to a further development of the invention, the new developmentof the solids discharge mechanism ensures that the undesired solidstransfer of already separated particles from the first dust collectingcontainer into the conical outer separating zone is completely preventedand that the particles sliding spirally downwards on the conicalcircumferential surface of the outer separating zone are transported introublefree manner into the first solids collecting container, withoutpassing through turbulent flow zones with return flows, which would leadto whirling up again.

As will be shown hereinafter by means of graphs, the inventiveconstruction of the cyclone separator leads to an increase in theoverall separation efficiency and the fraction separation efficiency,whilst simultaneously reducing the pressure drop compared withconventional cyclone construction. In particular, the diameter of thesmallest particles, which are 99% separated, is moved towards the 5 μmlimit, which corresponds to a separation efficiency of the inventivecyclone, which could not hitherto be achieved in practice by cycloneseparators. The average diameter of the particles which are 50%separated is 1 μm.

In order to improve the cyclone operating quantities, namely the overallseparation efficiency, the fraction separation efficiency and pressuredrop according to the invention it is not absolutely necessary to have aspiral cyclone intake channel in accordance with the describedembodiment and it is also in fact possible to use a tangential orhelical intake channel for the cyclone.

Further advantages, features and use possibilities of the invention canbe gathered from the following description of preferred embodiments inconjunction with the drawings, wherein show:

FIG. 1: A diagrammatic longitudinal section through a cyclone embodimentwith the inventive immersion tube column, the slit immersion tube havinga helical leading edge and a diffuser-type slit channel.

FIG. 2: A diagrammatic cross-section along section line II--II of FIG.1.

FIG. 3: A diagrammatic longitudinal section of a cyclone embodiment withthe inventive immersion tube column, the slit immersion tube beingprovided with four helically displaced intake channels with in each casea straight leading edge.

FIG. 4: A diagrammatic cross-section along section line II--II of FIG.3.

FIG. 5: A view of the inventive slit immersion tube with four helicallyreciprocally displaced intake channels with in each case a straightleading edge and a swirl promoter centred around the cyclone axis withinthe immersion tube column

FIG. 6: A cross-section through the inventive slit immersion tubeaccording to FIG. 5 along section line III--III of FIG. 3.

FIG. 7: A diagrammatic view of an inventive slit immersion tube with twoparallel-wall slit channels symmetrically arranged at the same axialheight and which are axially covered by upper and lower plates.

FIG. 8: A diagrammatic view of a slit immersion tube according to theinvention with a helical, parallel-wall slit channel, which isconstructed with a helical leading edge and helical trailing edge as afeed channel for the swirl promoter.

FIG. 9: The inventive two-stage solids discharge mechanism withshielding cone, which is arranged around the central immersion tubebelow the cylindrical shielding container.

FIG. 10: A diagrammatic representation of the flow profiles with axialand tangential velocity v_(z) and v₁₀₀, which form in the swirl promoterin the case of subcritical and supercritical swirling flow.

FIG. 11: Particle size distribution of the fines in the pure gas channelof the inventive cyclone separator (curve 25) compared with the particlesize distribution of the fines in the purse gas channel of the samecyclone separator without the inventive immersion the tube column (curve26).

The basic structure of the cyclone separator according to the inventionwith two separating zones and static guide mechanisms is constituted bya conventional cyclone. The four basic components shown in FIGS. 1 and3, namely the cyclone casing 12a, 12b, the spiral intake channel 11, thecylindrical immersion tube 5 and the solids collecting chamber 2a areconsequently also used as components of the cyclone separator accordingto the invention. In per se known manner, the cyclone casing comprisesan upper cylindrical outer jacket 12a and an axially downwardly taperingbottom conical outer jacket 12b, the cylindrical casing being higherthan the conical casing. Both jacket parts 12a, 12b surround the outerseparating zone 3a. Into the cylindrical outer separating zone projectsthe cylindrical immersion tube 5 centred around the cyclone axis 1 andwhich is used for removing the dedusted two-phase flow (gas+fines). Thetangential or spiral intake channel 11 serves to supply to the outerseparating zone 3a the accelerated two-phase flow (gas+feed) enteringthe cyclone. The lower conical cyclone jacket 12b ends, according toFIG. 3 on a cylindrical shielding container 20 with an annularclearance-like outlet 22 for the separated coarse material, which ismounted in the conventional solids collecting container 2a belowshielding container 20.

According to the inventive cyclone construction of FIGS. 1 and 3, theconventional immersion tube 5 is firstly axially extended by a slottedslit immersion tube 6, whose helical leading edge 9a (FIG. 1) orstraight leading edges 9b (FIG. 3), extend over the suction heighth_(i). Although suction by means of a slotted slit immersion tube isknown (DE-OS 32 23 374), the invention is constituted by the fact thatthe slit immersion tube 6 is open on its lower end face and has a slitchannel 10, which is used as the intake channel for an immersion tubecolumn, whose axis can be looked upon as the centre of the vortex core(cyclone eye). The arrangement of the bottom central immersion tube 7 inthe axial extension of the slit immersion tube 6 leads to the completeimmersion tube column 5, 6, 7 surrounding the complete separating zoneheight h and consequently can also be looked upon as a stabilizer forthe outer swirling flow in the separating zone 3a. The production of aninner swirling flow and therefore a following separation in the innerseparating zone 3b of the central immersion tube 7 (FIG. 4) or the swirlpromoter 17 (FIG. 3) are permitted by several parallel-wall slitchannels 10 uniformly distributed around the immersion tubecircumference (FIGS. 3 and 4), a slit channel 10 constructed as a curveddiffuser (FIG. 2) or a helical, parallel wall slit channel, eachparallel-wall channel bringing about a flow-accelerating action and canproduce a supercritical swirling flow. The outer swirling flow passesout on an outer portion of the central immersion tube 8 constructed as ashielding cone 4 and the inner swirling flow is centred about the swirlpromoter axis. 1. The central immersion tube 7 passes through theconventional solids collecting container 2a and is connected to a secondsolids collecting container 2b below the first container 2a in a gastight manner, so that no gas distribution is possible between the twocontainers.

In the cross-section of the inventive cyclone separator according toFIG. 1 shown in FIG. 2 a baffle 27 is provided below the tangentialintake channel 11 in the plane parallel to cyclone cover 15, in such away that an axially uniform inflow into the slit channel 10 withoutshort-circuit flows is ensured. Baffle 27 passes from the centre angleφ=0°, which is determined by the transition point of the outer wall ofintake channel 11 tangentially entering the cylindrical outer jacket 12of the cyclone casing, to the centre angle φ=180° as an annular collararound immersion tube 5. From there the leading edge of the baffle inthe rotation direction of the swirling flow passes roughly tangentiallyto the outer circumference of the annular collar up to the inner wall ofintake channel 11 on the underside thereof, whilst from there baffle 27completely covers the annular cross-section between the immersion tubecircumference and outer jacket 12 up to the centre angle φ=0° andterminates there in a radial edge running from the annular collarcircumference to the outer jacket 12. The outer opening of the slitchannel is located below the final portion of baffle 27. The annularcollar formed by the baffle prevents particles from being transported ina wall-near solids flow (boundary layer flow) on cyclone cover 13 andalong the outer circumferential surface of immersion tube 5 directlyinto the slit channel.

The cross-section of the inventive cyclone separator of FIG. 3 shown inFIG. 4 makes it possible to see the spiral inlet 11 of the cyclone andthe spiral outlet casing 8a necessary for energy recovery purposes witha central, conical recess core 8b, the slit immersion tube 6constituting an inflow guide mechanism for the outflow spiral 8. Theflow arrows indicate the equidirectional flow guidance or distributionbetween the cyclone intake and the cyclone outlet.

FIG. 5 is a view of an inventive slit immersion tube 6 with four intakechannels 10 reciprocally displaced along a helical line with in eachcase a straight, axial leading edge 9b, as well as a swirl promoter 17centred about cyclone axis 1 within the immersion tube column 5, 6, 7.Recesses 15 (cf. also FIG. 6) in the slit immersion tube 6 are in eachcase reciprocally displaced by 90°.

FIG. 6 shows the cross-section through the inventive slit immersion tube6 according to FIG. 5 with parallel-wall outer and inner contours of theslit channel 10. The entry area into slit channel 10 and its outlet areain swirl promoter 17 are spiral. The inflow into swirl promoter 17 takesplace exclusively by means of slit channel 10, so that any slit channelis provided with an upper and lower coverplate 19 for the ringcross-section between swirl promoter 17 and slit immersion tube 6.

If the slit immersion tube 6 is provided with two slit channels on thesame axial height corresponding to FIG. 7 or with a helically risingleading edge 9a and trailing edge 9c according to FIG. 8, then cycloneaxis 1 and swirl promoter axis are also identical, because there is aflow into swirl promoter 17 symmetrical to cyclone axis 1, so that ineach construction of the slit immersion tube 6 a wake area 16 is formeddue to the swirling flow and in it there are return flows 18.

FIG. 9 illustrates the inventive two-stage solid discharge device with ashielding cone 7, which is arranged around the central immersion tube 7below the cylindrical shielding container 20, which is placed betweenthe lower end of conical jacket 12b and the first solids collectingcontainer 2a. The shielding cone 4 with a downwardly projecting basesurface around the central immersion tube 7 is fixed to the latter andarranged within the primary solids collecting container 2a. A conical,downwardly widening deflecting shield 21 is arranged on the upper wallof container 4 following on to the cylindrical shielding container 20and prevents solids which have already been separated from whirling upagain. The second solids collecting container 2b is flanged in gas tightmanner to central immersion tube 7 below the primary solids collectingcontainer 2a.

FIG. 10 illustrates the different radial flow profiles of axialcomponent v_(z) and tangential component v₁₀₀ of the flow rate in swirlpromoter 17 in the case of subcritical and supercritical swirling flow23, 24, the return flow 18 in the case of supercritical swirling flowbrings about the transfer of the particles concentrated in the wake area16 in the second solids collecting container 2b.

FIG. 11 shows the improvement to the separating capacity obtained as aresult of the particle size distributions of the fines in the clean gaschannel of the inventive cyclone separator 25 compared with theconventional cyclone 26 without the immersion tube column 5, 6, 7according to the invention.

The cyclone separator embodiment according to FIG. 3 operates with thefollowing two-stage separating process.

The dust-containing gas sucked in by means of a compressor flows in perse known manner in the swirl-promoting intake channel 11 of the cycloneand via the latter into the cylindrical outer separating zone 3a, wherethe inflowing gas is uniformly sucked through the slit immersion tube 6over the suction heights h_(i) in the sense of the invention.

The flow in the cylindrical separating zone is a vortex sink. The gasflows on spiral paths with increasing velocity from the outside to theinside. The three-dimensional swirling flow produced makes it possibleon the one hand to produce the tangential velocity component of thecentrifugal acceleration required for separating purposes and on theother hand the axial velocity component transports the solids spirallyalong the outer cyclone jacket 12 into the primary solids collectingcontainer 2a, because fine dust particles do not follow the flow linesof the gas because, under the action of the high centrifugalaccelerations, they are passed out of the curved path against thecyclone jacket. The same secondary flows are observed on the separatingzone wall as in a teacup. This secondary flow along the wall of theconical separating zone 12b is, however, useful, because it also coversthe solids carried on the wall and leads same downwards to the solidscollecting container 2a. There is a solids stream on the concave wallsdue to the disturbed equilibrium of the compressive and centrifugalforces.

The tangential and radial component of the vortex sink flow, whosevelocity profile on the slit immersion tube 6 is constant over theheight of the suction slit h_(i), are sucked in between the outer andinner contours of the slit channel 10, so that the particles in theouter field of flow of cyclone 3a are forced to separate under constantconditions. As the dimensioning of the leading face of the slitimmersion tube 6 takes place in such a way that the vortex sink flow inthe outer separating zone 3a is not disturbed, there is a powerfulvortex field around the immersion tube column 5, 6, 7, so that highcentrifugal forces are made to act on the particles in the separatingzone.

The gas flow sucked in via slit channel 10 from the primary separatingzone 3a is then deflected on to the outer circumferential surface of theswirl promoter 17, in which is formed a second inner swirling field withthe vortex core 16 of the cyclone, so that the secondary separatingeffect is initiated. According to FIG. 10 this inner swirling flow onlyhas a two-dimensional field of flow, because there is no longer anyradial velocity component (sink flow). As a result of the swirling flowwithin swirl promoter 17, ultra-fine particles stil suspended in the gasflow are "trapped" in the wake core 16 and are transported into thesecondary solids collecting container 12 with the aid of the downwardlydirected axial component 18. As a result of the central immersion tube 7the particles have an adequate axial clearance, in order to arrive inareas where all the flow components have died away, but there are stillstrong tangential velocity components.

As in any curved flow, the static pressure drops in marked manner fromthe outside to the inside in the swirl promoter 17. The lowest pressureof the vortex prevails in the swirl promoter axis or cyclone axis 1.Thus, the compressive force acting on the particles is much higher thanthe centrifugal force, so that the strong secondary flows inwardstowards cyclone axis 1 aid the secondary separating effect. The solidslayers initially bound by the swirl promoter inner wall are displacedtowards the radial pressure gradient, whilst the cleaned through flow 23flows along the inner swirl promoter walls.

In the case of a powerful vortex, which is sought by a correspondinginventive immersion tube intake construction, the flow concentrates on anarrow outer annular zone in swirl promoter 17. The axial velocitycomponent v_(z) and the radius of the wake core R₀ become larger, of.FIG. 10. The swirl is no longer constant over radius r and velocitypeaks 23, 24 form. According to FIG. 10, there is a reduction to theaxial velocity v_(z) in cyclone axis 1.

According to the laws of hydrodynamic equilibrium, in the case of aconstant through flow, there is a physical dependence between the vacuumforce, axial component v_(z) and swirl intensity and this is onlymodified by the critical swirl. By increasing the latter a vacuum forceminimum is compared with a kinetic energy minimum. This swirl increaseallows the vacuum to increase to such an extent that there is a returnflow 18 of the axial velocity within the vortex core 16. This phenomenonin which the swirling flow without an inner axial return flow in thewake core reverses into a swirling flow with an axial return flow 18along the cyclone axis 1, is used for particle separation purposeswithin the swirl promoter 17. This sought flow reversal with maximumreturn flow is obtained in the case of high swirl and brings about thetransporting away of the particles in the wake area 16, which are kepttrapped as a result of the radial pressure drop in said area 16.

The different behavior of the flows with weak and strong swirl alongcyclone axis 1, particularly within the slit immersion tube 6, can beattributed to the different pressure changes, which in the case of flowswith a strong swirl bring about an internal return flow 18 from the slitimmersion tube 6 to the following central immersion tube 7 or thesecondary solids collecting container 2b. A slit immersion tube 6bringing about this phenomenon of the return flows is fundamentallysuitable for utilizing the secondary separating effect for dustseparation from a flowing fluid.

Whereas the primary separating process in the outer separating zone 3ais based on the action of centrifugal forces on the particles, as in theconventional cyclone, for bringing about the secondary separatingprocess within the swirl promoter use must be made of the flow reversalphenomenon for particle separation from a flowing fluid. This bringsabout a two-stage separation of particles suspended in two-phase flowsin a single apparatus.

The kinetic energy of the swirling flow is recovered by an outflowspiral 8a with recess core dimensioned in known manner and arranged aboethe cyclone cover 13, so that both the axial component and thetangential component of the inner swirling flow are delayed in such away that the cyclone entry velocity and cyclone exit velocity assume thesame values for the same tube cross-sections of the raw gas and pure gaschannel.

The effectiveness of the described two-stage separating process has beenconfirmed by numerous experiments on a cyclone test installation undernear practical conditions. The reduction of the coarse-grain materialproportion of the fines in the pure gas channel by incorporatinginventive immersion tube column around the cyclone axis compared with aconventional cyclone construction without additional guide andseparating mechanism is shown by FIG. 11 by means of comparativeparticle size analyses of the fines, the feed being constituted byquartz powder with an average particle size diameter of 6 μm. It can inparticular be established that not only is there an increase in theoverall separation efficiency and that the solids concentration in thepure gas channel decreases, but there is also a decisive improvement tothe fraction separation efficiency, because the smallest particle sizeof 15 μm separated by 90% is displaced far into the finer particle sizerange of 2 μm.

Through the use of the invention the field of use of cyclone separatorsis greatly widened. A possible future use of the inventive cyclone isremoving the dust from a pressure-operated fluidized bed firing systemor furnace in a combined gas/steam turbine plant. The gas turbine planesare subject to both erosive and corrosive wear, so that the erosionaction has a marked effect as from a particle diameter of d≧10 μm. Inaddition, the air/flue gas-side pressure loss of the combined processconsiderably influences the process efficiency.

I claim:
 1. Cyclone separator comprising two separating zones (3a, 3b)and static guide mechanisms for improving the separating capacity withrespect to very finely dispersed particles from flowing gases andreducing the pressure drop or for influencing the field of flow of acentrifugal force separator with a tangential, spiral or helical intakechannel (11), including an upper cylindrical (12a) and a lower conical(12b) cyclone casing, a solids collecting container (2a) located belowit, whilst in the cylindrical separating zone, a cylindrical immersiontube (5) for removing the pure gas flow projects centrally from aboveinto the cyclone casing, including an immersion tube column comprising aseries connection of the immersion tube (5), a slotted slit immersiontube (6) with a helical or straight slit channel and a central immersiontube (7), by which the cyclone axis (1) is surrounded over the entireseparating zone height h, is located in the cylindrical interface of thecyclone separator, passes through the solid collecting container (2a)and is connected in gas tight manner to a second solids collectingcontainer (2b) located below the first container, means for enabling thethree partial immersion tubes (5, 6, 7) to be connected in reciprocallyopen manner and the slit immersion tube (6) is the sole sucking partialimmersion tube.
 2. Cyclone separator according to claim 1, characterizedin that between the intake channel (11) and the slit immersion tube (6)is provided a baffle (27) protecting the latter against short-circuitflows.
 3. Cyclone separator according to claim 2, characterized in thatthe baffle (27) on the immersion tube (5) below the cyclone intakechannel (11) is installed in the outer separating zone (3a) in thehorizontal plane parallel to cyclone cover (13), so that short-circuitflows of the swirling flow are directly prevented in the suction channel(10) of the slit immersion tube (6) and the axial velocity component ofthe swirling flow is positively influenced with respect to the solidsdischarge behaviour in the outer separating zone (3a).
 4. Cycloneseparator according to one of the claims 1 to 3, characterized in thatthe sole sucking slit immersion tube (6) is constructed as aflow-favourable intake guide mechanism for an outlet spiral casing (8a)with recess core (8b) positioned above the cyclone cover (13). 5.Cyclone separator according to one of the claims 1 to 4, characterizedin that the intake face of the parallel-wall slit channel (10) of theslit immersion tube (6) is constructed as a slotted opening within theslit immersion tube jacket in such a way that in the intake region ofthe slit channel the requisite flow velocity is set on the interface inaccordance with the rotary sink flow present and is in turn capped bythe configuration of the slit immersion tube circumference as alogarithmic spiral (15) in flow-favourable manner on the interface, sothat the curved flow lines of the gas flow entering through the slitchannel (10) into swirl promoter (17) pass along the outer and innerslit channel contour and in the same direction as the cyclone entryflow.
 6. Cyclone separator according to claim 1, characterized in thatthe slit immersion tube (6) is provided with four parallel-wall intakechannels (10) uniformly distributed around the immersion tubecircumference and with in each case a straight leading edge (9), so thatthe common diagonal (14) of the four recess faces (15) displaced by 90°forms a single helical line about the slit immersion tube (6) as anintake channel with an accelerating flow action for a swirl promotor(17) symmetrical to cyclone axis (1), so that within the swirl promoter(17) a wake area (16) forms with axial return flows (18) into thecentral immersion tube (7) in the case of correspondingly high swirlintensity, being fixed by the geometrical design of the slit channel(10) and the slit immersion tube (6), high vacuum values on the cycloneaxis (1) and strong pressure changes in the axial direction inducing theintense return flow (18) into central immersion tube (7) andsubsequently into the secondary solids collecting container (2b). 7.Cyclone separator according to one of claims 1 and 6, characterized inthat for increasing the rotational symmetry and swirl intensity the slitimmersion tube (6) with four intake channels (10) helically distributedabout the immersion tube circumference is replaced by a slit immersiontube provided either with several slit channels (10) uniformlydistributed at the same axial height around the immersion tubecircumference and in each case having a straight leading edge (9b) orwith a parallel-wall, helical slit channel (10), which has a helicalleading edge (9a) and a helical trailing edge (9c), so that asupercritical swirl intensity with return flows (18) into the centralimmersion tube (7) is produced if the particular slit channel (10) isconstructed as a curved deflecting channel with an accelerating actionand the particular slit channel (10) is provided with an upper and alower coverplate (19), so that the suction from the outer separatingzone (3a) takes place exclusively by means of a helical slit channel orby means of several slit channels uniformly distributed edgewise on theimmersion tube circumference.
 8. Cyclone separator according to one ofthe claims 1 to 7, characterized in that a cylindrical shieldingcontainer (20) is interposed between the conical part (12b) of the outerseparating zone (3a) and the first solids collecting container (2a), sothat the outer swirl flow ends on an outer portion of the centralimmersion tube (7) constructed as a shielding cone (4) within the firstsolids collecting container (2a), so that the separated solids canpenetrate the first solids collecting container (2a) in troublefreemanner and without entraining effects in the annular clearance 922)between the cylindrical shielding container (20) and the centralimmersion tube (7) and through the arrangement of a conical deflectingshield (21) below the cylindrical shielding container (20) and about theshielding cone (4) the solids cannot be whirled into the outerseparating zone (3a) again